输入基底对深厚土层地震反应影响分析

Effect of Input Basement on Seismic Response of Deep Soil Deposit

对于孔深达到100m,但剪切波速低于500m/s的深厚土层,首先论述了计算其地震反应时输入基底的常用处理方法,然后基于理论分析和工程实例,建立了3个输入基底(线性外推、软弱夹层假定、坚硬基底)模型,结合土层非线性试验数据,使用一维等效线性化程序计算了不同强度地震作用下各模型的反应。对地表加速度峰值和反应谱进行了对比分析,指出坚硬基底模型建模简单,结果偏安全,适于工程应用。最后,通过多个基底波速值对地表反应影响的敏感性分析,提出了坚硬基底剪切波速的合理取值为相邻土层波速值的1.3~1.4倍,且不低于500m/s。

To the deep soil deposit,for which the shear velocity is less 500m/s,while the burial depth is 100 m,the present methods dealing with the basement in seismic response computation are discussed.Based on theoretical analysis and engineering cases,3basement models（linear extrapolation,soft interlayer assumption and stiff basement）are made.The models＇ dynamic response under different seismic intensity is calculated by 1Dequivalent linearization routines and the relative soil nonlinear parameters are provided by experiments.The PGA and response spectra are compared and the results show the stiff basement model is more favorable in engineering application,which is simple and compatible.The effect of wave velocity of stiff basement on seismic response is numerically analyzed and a proper wave velocity ratio between upper soil and basement is recommended.